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CHEMICAL ENGINEERING (187 journals)                     

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AATCC Journal of Research     Full-text available via subscription   (Followers: 3)
ACS Sustainable Chemistry & Engineering     Hybrid Journal  
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 7)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 12)
Advanced Powder Technology     Hybrid Journal   (Followers: 12)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 4)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 20)
Advances in Chemical Engineering and Science     Open Access   (Followers: 31)
Advances in Polymer Technology     Hybrid Journal   (Followers: 12)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 8)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 5)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 12)
Biofuel Research Journal     Open Access   (Followers: 3)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 8)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 7)
Catalysts     Open Access   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription  
Chemical and Engineering News     Free   (Followers: 10)
Chemical and Materials Engineering     Open Access   (Followers: 3)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 9)
Chemical and Process Engineering     Open Access   (Followers: 5)
Chemical and Process Engineering Research     Open Access   (Followers: 7)
Chemical Communications     Full-text available via subscription   (Followers: 62)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 30)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 14)
Chemical Engineering and Science     Open Access   (Followers: 5)
Chemical Engineering Communications     Hybrid Journal   (Followers: 11)
Chemical Engineering Journal     Hybrid Journal   (Followers: 21)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 19)
Chemical Engineering Research Bulletin     Open Access   (Followers: 2)
Chemical Engineering Science     Hybrid Journal   (Followers: 19)
Chemical Geology     Hybrid Journal   (Followers: 12)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 122)
Chemical Society Reviews     Full-text available via subscription   (Followers: 36)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 4)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 135)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
ChemSusChem     Hybrid Journal   (Followers: 6)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 10)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 19)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 3)
Crystal Research and Technology     Hybrid Journal   (Followers: 5)
Current Opinion in Chemical Engineering     Open Access   (Followers: 4)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 40)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 1)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 4)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Info Chimie Magazine     Full-text available via subscription   (Followers: 2)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 2)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 2)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 4)
International Journal of Waste Resources     Open Access   (Followers: 3)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 4)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 10)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 100)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 10)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 5)
Journal of Chemical Engineering     Open Access   (Followers: 6)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 1)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 13)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 1)
Journal of Coatings     Open Access   (Followers: 4)
Journal of Crystallization Process and Technology     Open Access   (Followers: 5)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 1)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access  
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Fuels     Open Access  
Journal of Geochemical Exploration     Hybrid Journal  
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal  
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 6)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 5)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 7)
Journal of Ocean University of China (English Edition)     Hybrid Journal  
Journal of Organic Semiconductors     Open Access   (Followers: 4)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 4)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 8)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 5)
Journal of Polymers     Open Access   (Followers: 2)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Powder Technology     Open Access   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 221)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 6)
Jurnal Inovasi Pendidikan Kimia     Open Access  
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 15)
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Molecular Imprinting     Open Access  
MRS Communications     Hybrid Journal  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 2)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 3)
Plasma Processes and Polymers     Hybrid Journal  
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 83)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 13)
Powder Technology     Hybrid Journal   (Followers: 12)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 54)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Full-text available via subscription   (Followers: 2)
South African Journal of Chemistry     Full-text available via subscription   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 6)
Sustainable Chemical Processes     Open Access   (Followers: 1)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 2)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 1)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)


Journal Cover Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [19 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2817 journals]
  • On wetting characteristics of droplet on a spherical particle in film
           boiling regime
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Subhasish Mitra, Thi Bang Tuyen Nguyen, Elham Doroodchi, Vishnu Pareek, Jyeshtharaj Bhalchandra Joshi, Geoffrey Michael Evans
      This study reports droplet-particle interaction of size ratio less than unity in the film boiling regime on a highly thermally conductive spherical particle surface. Specifically, the effects of impact Weber number (We) of subcooled state droplets comprising water (We=3.9–103.6) and isopropyl alcohol (IPA) (We=8.6–194.6) were studied using high speed imaging technique in the particle temperature range of 250–350°C. In general, non-wetting interaction behaviour was observed with two distinct outcomes – rebound and complete disintegration demarcated by a critical Weber number range instead of a single threshold value. Extent of surface wetting was characterised by the maximum droplet spread diameter parameter which was found to scale with impact Weber number in a power law form which agrees with the theoretical scaling argument. Additionally, an energy balance model was developed to compute this parameter which provided good agreement with the experimental measurements in the lower Weber number regime, however, higher deviations were noted near the transition regime. Also quantified from experiments was the droplet-particle contact time which exhibited a power law dependency on Weber number in the rebound regime, however, was noted to be almost independent of Weber number in the disintegration regime. Particle surface wettability was characterised by the experimentally measured dynamic contact angles which were found to vary in the range of 120–160o in low Weber number regime manifesting the hydrophobic nature of particle surface in film boiling regime. Also, all the parameters such as contact line velocity, particle temperature and droplet size apparently had relatively insignificant influence on the variation of dynamic contact angle. Temporal variation of non-dimensional spreading parameter exhibited a self-similar behaviour wherein all data collapsed on a single power law profile. It was further shown that the behaviour could also be described by a recovery type exponential profile through suitable non-dimensionalization and both profiles can be utilized to produce a spreading kinetics.
      Graphical abstract image

      PubDate: 2016-04-28T01:20:15Z
  • Three dimensional flow of liquid transfer between a cavity and a moving
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Diego M. Campana, Sebastián Ubal, María D. Giavedoni, Fernando A. Saita, Marcio S. Carvalho
      Gravure printing is one of the most promising technologies for high volume production of printed electronics and microscale films and devices. The characteristics of the printed pattern, i.e. ink volume, resolution and pattern placement (registration), are directly related to the fluid mechanics of the liquid transfer process from a cell to a substrate wrapped around a rotating roll; the liquid transfer is mainly controlled by free surfaces and dynamic contact lines. Most of the available analyses are restricted to axisymmetric flows, at which the relative motion between the cavity and the substrate is greatly simplified. Recent results have shown that the use of the complete description of the relative motion in a roll-to-roll process is critical to obtain accurate results on the amount of liquid that is transferred to the substrate. In this work we present an extension of the model describing liquid transfer from a groove to a substrate in a R2R process in order to consider the liquid transfer from a small individual cell; to this end we solve a full 3D free surface flow with moving contact lines. The results show that the liquid transfer dynamics is governed by two different characteristic time scales, one is associated with the contact line motion and the other with liquid filament breakup. Both are dependent on the capillary number. The predictions show how the volume, registration and shape of the printed dot varies with operating conditions and liquid properties. These predictions could be helpful in designing high precision printing operations.
      Graphical abstract image Highlights

      PubDate: 2016-04-28T01:20:15Z
  • Ultra-fast microfluidic mixing by soft-wall turbulence
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): V. Kumaran, P. Bandaru
      Slow cross-stream mixing in micro-fluidic devices poses a significant challenge in realising efficient lab-on-a-chip technologies. Due to the small dimension and flow velocity, the flow is in the laminar regime, and this results in slow molecular cross-stream diffusion (in contrast to the fast turbulent mixing by cross-stream eddies in industrial applications). Here, we demonstrate a simple and powerful strategy for ultra-fast mixing in a microchannel with one soft wall with height as low as 35μm at a Reynolds number as low as 226. There is a spontaneous transition from a laminar flow to a turbulent flow state when the flow rate increases beyond a threshold value, resulting in complete cross-stream mixing. After transition, the mixing time across a channel of width 0.5mm is smaller, by a factor of 105, than that for a laminar flow, and complete mixing is achieved within a channel length of 2cm. The increased mixing rate comes at very little energy cost, because the pressure drop is comparable to that required in current microfluidic devices, and it increases continuously and modestly at transition. This is because the channel length required to achieve complete mixing, 2cm, is much smaller than that used in microfluidic devices that employ diffusive mixing; in addition, the deformation of the soft wall decreases the resistance to flow.

      PubDate: 2016-04-28T01:20:15Z
  • Monte Carlo simulations of phase equilibria and microstructure of
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Yongping Zeng, Jie Jin, Chunfeng Wang, Yueyang Xu, Jilong Wang, Shengui Ju
      Monte Carlo simulations were carried out to calculate the phase behavior of thiophene in the binary and ternary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) and carbon dioxide using a united atom model. The calculated pure ionic liquid densities and structural properties of [Bmim][PF6] as well as the vapor pressure of thiophene in the ionic liquid were compared with the available experimental data in the literatures, and a good agreement was obtained. Based on the radial distribution functions (RDFs) and spatial distribution functions (SDFs) results, thiophene molecules prefer to organize around the C10 atom of the butyl chain connected with the imidazolium ring. The concept of local composition in solutions was used to better understand the solution structure. It is shown that thiophene molecules can strongly associate with the cation. For the ternary system of CO2/thiophene/IL, CO2 can affect the solubility of thiophene in ionic liquid when the pressure is changed. CO2 molecules interact with the anion stronger than thiophene molecules. This implies that CO2 can be used as a potential recovery desorbent of thiophenic compounds in the ionic liquid by tuning the pressure.

      PubDate: 2016-04-28T01:20:15Z
  • A study of wavy falling film flow on micro-baffled plate
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Hideaki Ishikawa, Shinichi Ookawara, Shiro Yoshikawa
      The effects of baffles, flow conditions and fluid properties on wavy motion of falling film were examined experimentally and numerically. Visualization showed that the liquid film became wavier by increasing the baffle distance and by changing liquid from water to methanol in the range of Reynolds number less than 42. Subsequently, the falling film behavior was numerically investigated by adopting VOF method. The qualitative agreements under similar flow conditions well validated both of visualization and numerical methods. The numerical results showed that a higher baffle tended to cause film break-up while the break-up was prevented by increasing the flow rates. As Reynolds number increases, the liquid film became wavier and further surface deformation became obvious. Those results demonstrated that properly-baffled reaction plate could form a noticeably wavy and deformed but quasi-stable falling film at a given flow rate for an organic solvent. The amplitude of wavy falling film on the baffled plates was correlated with Reynolds number, Bond number and non-dimensional geometrical factors, while the thickness of the wavy falling film was correlated with the non-dimensional geometrical factors. It was finally suggested that the possible enhancement of gas absorption due to the surface deformation of liquid film is of further interest targeting process intensification.
      Graphical abstract image

      PubDate: 2016-04-28T01:20:15Z
  • Hydrodynamic effects on three phase micro-packed bed reactor performance
           – Gold–palladium catalysed benzyl alcohol oxidation
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Noor Al-Rifai, Federico Galvanin, Moataz Morad, Enhong Cao, Stefano Cattaneo, Meenakshisundaram Sankar, Vivek Dua, Graham Hutchings, Asterios Gavriilidis
      The hydrodynamics of a three-phase micro-packed bed reactor and its effect on catalysed benzyl alcohol oxidation with pure oxygen were studied in a silicon–glass microstructured reactor. The microreactor was operated at 120°C and 1barg and contained a channel with a 300μm×600μm cross-section, packed with 1wt% Au–Pd/TiO2 catalyst, 65μm in average diameter. Improvements in the conversion of benzyl alcohol and selectivity to benzaldehyde were observed with increasing gas-to-liquid ratio, which coincided with a change in the flow pattern from a liquid-dominated slug to a gas-continuous flow regime. The observed enhancement is attributed to improved external mass transfer, associated with an increase in the gas–liquid interfacial area and reduction in the liquid film thickness that occur with gradual changes in the flow pattern. A maximum selectivity of 93% to benzaldehyde was obtained under partial wetting – which introduced the added benefit of direct gas–solid mass transfer – outperforming the selectivity in a conventional glass stirred reactor. However, this was at the expense of a reduction in the conversion. A response surface model was developed and then used to predict optimal operating conditions for maximum benzaldehyde yield, which were in the gas-continuous flow regime. This corresponded to relatively high gas flow rate in conjunction with moderate liquid flow rate, ensuring sufficient catalyst wetting with a thin film to reduce transport resistances.
      Graphical abstract image

      PubDate: 2016-04-28T01:20:15Z
  • Optimum synthesis of an electrodialysis framework with a Background
           Process II: Optimization and synthesis of a water network
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Chiedza Demetria Nezungai, Thokozani Majozi
      The water-energy nexus considers the relationship between water and energy resources. The tightening environmental regulations and social pressures have made it necessary to develop processes that are conservative with respect to both these resources. In the first part of this series, a multi-contaminant electrodialysis (ED) model was developed. In this second part of the series, the application of the developed ED model for the partial purification of contaminated water within a water network synthesis (WNS) and optimization problem is explored. The optimization model is based on a superstructure framework, where the objective is to minimize freshwater consumption, wastewater production, energy consumption and the operating and capital costs involved in the process integration. A comparison is made between the framework presented in this manuscript and the more common black box model, which simplifies regeneration units to linear expressions. The results show that the black box approach can lead to inaccuracies of up to 85% in the costing of regeneration units. ED optimization performed within the WNS problem results in a more comprehensive design than if the design is developed as a standalone model. Furthermore, it is shown that there are significant environmental and financial benefits in the simultaneous minimization of water and energy in water networks. When applied to a pulp and paper case study, the integrated approach resulted in 38% reduction in total freshwater consumption and 67% savings in wastewater treatment costs.

      PubDate: 2016-04-23T22:17:30Z
  • Optimum synthesis of an electrodialysis framework with a background
           process—I: A novel electrodialysis model
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Chiedza D. Nezungai, Thokozani Majozi
      Electrodialysis (ED) is a membrane process commonly employed for the desalination of brine or water contaminated by ionic components. The driving force for desalination is the potential difference between the contaminated and purified water. Despite its ability to produce ultra-pure products, the application of electrodialysis is exceeded by other treatment processes, due to its energy intensity. Energy consumption in ED is dependent on the physical characteristics of the unit. In this respect, it is possible to promote the use of electrodialysis by optimizing the process, making it more energy efficient. This can be done by developing an optimization framework for the process. Existing electrodialysis design models, based on current density, cater mainly for the desalination of brine. This paper presents a detailed derivation for a single stage electrodialysis design model, suitable for treating a binary mixture of simple salts. A simplified formulation is also presented, based on the assumption that the conductivity of the solution is constant over the entire unit. This simplifying assumption enables more versatile application of the ED design model with background processes. Using a pulp and paper case study, a comparison is done between the two models, indicating a deviation of less than 2% in all key variables. It is therefore possible to reliably use either of the models interchangeably, depending on the available information and the background process under consideration. Both models presented are mixed integer nonlinear programs (MINLP) solved using a combination of DICOPT and BARON solvers in GAMS®.

      PubDate: 2016-04-23T22:17:30Z
  • Editorial Board
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147

      PubDate: 2016-04-23T22:17:30Z
  • Table of Contents
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147

      PubDate: 2016-04-23T22:17:30Z
  • Numerical modeling of anisotropic drag for a perforated plate with
           cylindrical holes
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Youngmin Bae, Young In Kim
      Direct numerical simulations of an incompressible laminar flow past a perforated plate are carried out at the pore scale. With the aim of evaluating the anisotropic drag of a perforated plate, two simple flow tests have been conducted: i) transpiration flow through a perforated plate with a regular array of cylindrical holes and ii) a linear shear flow over the plate. In the transpiration flow test, the dependence of the pressure drop on the transpiration velocity is discussed for porosities of 0.1–0.4 and hole depth to diameter ratios of 1–3 at pore-level Reynolds numbers of up to 25. The linear shear flow problem is then investigated along with a discussion of the effects of porosity, plate thickness, and pore distribution on the slip velocity at a clear fluid/perforated plate interface. Simple correlations of directional permeabilities and non-Darcy coefficients are also proposed for the perforated plate, with their application to a lid-driven cavity flow.

      PubDate: 2016-04-23T22:17:30Z
  • Enhancing natural product extraction and mass transfer using selective
           microwave heating
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Chai Siah Lee, Eleanor Binner, Charles Winkworth-Smith, Rebecca John, Rachel Gomes, John Robinson
      This study uses a combination of empirical observations and an analysis of mass transfer behaviour to yield new insights into the mechanism of microwave assisted extraction. Enhancements in extraction rate and yield were observed experimentally compared with conventional extraction at temperatures in excess of 50°C, however at lower temperatures there was no observable difference between the two processes. A step-change in extract yield between microwave and conventional processes was shown to be caused by selective heating. A temperature gradient of the order of 1°C is sufficient to reduce the water chemical potential within the cell structure, which changes the osmotic potential such that internal cell pressures can increase to the point where disruption occurs. This paper demonstrates the need to operate microwave extraction processes at a temperature that enables selective heating, and a newly-proposed mass transfer phenomenon that could have wider positive implications for extraction and leaching processes.
      Graphical abstract image

      PubDate: 2016-04-23T22:17:30Z
  • A simulation study on the conversion efficiency of catalytically active
           particulate filters
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): B. Opitz, M. Votsmeier
      A catalytically active particulate filter with a first order catalytic reaction taking place inside the filter walls is investigated by numerical simulation. The conversion efficiency for different channel geometries and operating conditions is systematically studied as a function of the governing dimensionless parameters. It is found that the conversion efficiency of a catalytically coated wall flow filter is very close to that of an ideal plug flow reactor over the full range of realistic operating conditions. Only in a range of intermediate residence times, the filter reactor shows some diffusion limitation which leads to conversion efficiencies slightly below that of the plug flow reactor. In all cases, these deviations from ideal conversion behaviour are below 15%. If the filter and the open monolith are compared at identical operating conditions and channel geometries, for fast reactions, the filter reactor shows higher conversion efficiency than the open monolith, since in this case the open monolith becomes strongly mass transfer limited. However, there can be a small range of conditions where the monolith is slightly more efficient than the filter. The reason for this effect is that due to the thinner washcoat layer the onset of mass transfer limitation in the coated monolith is shifted to higher reaction rates, compared to the filter reactor.

      PubDate: 2016-04-23T22:17:30Z
  • Two-fluid simulation of liquid drainage in oscillating packed beds for
           offshore floating applications
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Ion Iliuta, Faïçal Larachi
      Three-dimensional modeling of liquid drainage dynamics in vertical, inclined and oscillating packed bed reactors is virtually inexistent in the literature. An attempt was made in this work where liquid drainage dynamics in vertical, inclined and oscillating packed bed reactors was analyzed via an unsteady-state three-dimensional two-fluid hydrodynamic model. Angular oscillations of the packed bed reactor between two angled symmetrical positions and between vertical and inclined position were considered while bed non-uniformity was described using radial porosity distributions. The simulation results highlighted the fully interpretable trends of the transient liquid flow in packed beds and underlined the differences in the transient behavior of the vertical, inclined and oscillating packed bed reactors. Although the initial period of liquid drainage was dominated by gravity regardless of bed configuration, the packed bed angle with respect to gravity direction had a significant impact on the liquid drainage dynamics. Cross-sections along streamwise direction both for static and oscillating inclined positions of the bed highlighted gas-rich uppermost and liquid-rich lowermost domains. Unlike vertical beds for which drainage occurred according to a quasi-plug flow of the liquid core region, drainage of inclined beds underlined 3D liquid flow structures with liquid-rich lowermost cross-sections which accelerated liquid withdrawal. Compared to the inclined bed case, liquid drainage was delayed under oscillating regimes as a result of reverse secondary flows induced by the column motion. The initial drainage process was controlled by the liquid flow in the bed lowermost part whereas oscillations between two symmetrically angled positions led to almost cross-sectionally uniform liquid drainage distribution. This is valuable and it is plausible that at long time the performance of packed bed reactors onboard offshore floating nonstationary platforms is insignificantly affected by the oscillations between two symmetrically angled positions.

      PubDate: 2016-04-23T22:17:30Z
  • Analysis of di-methyl ether production routes: Process performance
           evaluations at various syngas compositions
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Minh Tri Luu, Dia Milani, Matthew Wake, Ali Abbas
      This paper investigates direct di-methyl ether (DME) production based on dry methane reforming (DMR-to-DME) and on bireforming (BiR-to-DME). Technically, DMR-to-DME is preferred to BiR-to-DME because the former produces synthesis gas (syngas) with a hydrogen to carbon monoxide molar ratio (H2/CO) of 1 which is the ideal ratio for DME synthesis. Whereas the latter produces a H2/CO close to 2 and consequently suffers from two apparent drawbacks: (1) lack of the so-called ‘synergy effect’ – a feature that enhances DME yield when operating at H2/CO close to 1, and (2) generation of a high heat capacity by-product (H2O) which makes DME recovery energy intensive. In this paper, we find that those two disadvantages actually enhance the performance of BiR compared to DMR across a range of performance metrics. Although the presence of water increases the cooling/heating duty and the distillation columns’ reboiler duty in the BiR route, more heat released from DME synthesis reactor can be utilized in the reboilers to make BiR techno-economically compatible. To assess the sustainability of DMR and BiR, evaluations are carried out against an existing industrial scale DME production route (auto-thermal-reforming (ATR)). By utilizing the carbon in the CO2 from an attached post-combustion carbon capture plant, DMR and BiR can save 22.3% methane feed uptake on average compared to the ATR process, which results in the DMR and BiR reducing CO2 emissions by at least 6.5% on average.

      PubDate: 2016-04-23T22:17:30Z
  • Multiphase reactive-transport simulations for estimation and robust
           optimization of the field scale production of microbially enhanced coalbed
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Gouthami Senthamaraikkannan, Ian Gates, Vinay Prasad
      The discovery that approximately 20% of natural gas is microbial in origin has elevated interest in microbially enhanced coalbed methane (MECoM). However, a rational approach to exploit this calls for the development of reservoir scale models that include the effect of microbial activity. To address this, we have developed a multiscale, multiphase, multicomponent reactive-transport model for the production of microbially enhanced coalbed methane (MECoM) that includes microbial kinetics. The model is used to evaluate field scale strategies for commercial MECoM production. Optimization studies are also conducted over a range of compositions of the injected nutrient and injector bottomhole pressures. In order to account for the effect of uncertainty in the model parameters, mean-variance robust optimization is performed, allowing a trade-off between performance and robustness. Proxy modeling is performed in a multivariate polynomial chaos expansion framework to evaluate the cost functions involved in the robust optimization and sparse expansions are constructed in order to deal with issues related to high dimensionality. The optimization strategy is tested for different trade-offs between robustness and performance. It is observed that for the given case, the location of robust optimal points does not vary unless only robustness is included in the objective function, and nominal performance is not.

      PubDate: 2016-04-23T22:17:30Z
  • A novel backlight fiber optical probe and image algorithms for real time
           size-shape analysis during crystallization
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Toufic El Arnaout, P.J. Cullen, Carl Sullivan
      Process analytical technology requires not only process suitable sensors, but also novel data processing approaches in order to make real time analysis feasible. In this paper, a novel in-line probe was designed, fabricated and tested for crystallization monitoring. The design benefits from state of the art optics and camera, fiber backlight illumination, and an optimized depth of focus and field of view. Image analysis steps to study both crystal size and shape are presented. These image analysis algorithms do not require manual-thresholding of individual images or time zero image subtraction, due to the use of a ‘rolling ball’ self-adapting background correction step. The approach is tolerant to blank images, noise, blurriness, out of focus objects, and common spatial or intensity variations. The method developed should help in the identification of changes in size and shape in crystal populations. Examples are presented for glass sphere standards, the crystallization of d-mannitol and l-glutamic acid, as well as an engineered needle-sphere mixture. A data binning strategy useful for future studies is also reported. The ultimate goal is control of crystallization under the Process Analytical Technology framework.

      PubDate: 2016-04-20T16:31:25Z
  • Inkjet printing of ceramic colloidal suspensions: Filament growth and
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Marguerite Bienia, Martine Lejeune, Michaël Chambon, Valérie Baco-Carles, Chrystelle Dossou-Yovo, Rémi Noguera, Fabrice Rossignol
      Filament growth and breakup are investigated in the context of ceramic inkjet printing. Several inks were formulated and ejected on a printer dedicated to ceramic materials. They consisted of six colloidal inks, four simple fluids and two graphic inks. For each, stroboscopic snapshots were acquired and the filament shape was extracted and analysed, for different nozzle actuation pulses. The filament length and the thread minimum radius were measured during the ejection process. A scaling of the breakup time with the Rayleigh number was obtained, as well as a general behaviour for the filament growth rate during the ejection process.
      Graphical abstract image Highlights

      PubDate: 2016-04-20T16:31:25Z
  • Classical density functional theory for gas separation in nanoporous
           materials and its application to CH4/H2 separation
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Fangyuan Guo, Yu Liu, Jun Hu, Honglai Liu, Ying Hu
      Three-dimensional classical density functional theory (CDFT) has been introduced and applied to predicting gas separation in metal-organic frameworks (MOFs). The formula of CDFT is based on modified fundamental measure theory (MFMT) and mean field approximation (MFA). The accuracy of the theory has been examined by simulations, and it has been implemented into a high-throughput screening of CH4/H2 separation materials. A total of 1200 MOFs have been examined, with selectivity ranging from 70 to 220 depending on the temperature, pressure and bulk CH4/H2 ratio, which is much higher than that of real MOFs. A set of promising CH4/H2 separation MOFs has been identified. According to the analysis of the isotherm and density profile, a MOF material with a pore size that can accommodate only one CH4 molecule seems to be the best for CH4/H2 separation.

      PubDate: 2016-04-20T16:31:25Z
  • Advanced millireactor technology for the kinetic investigation of very
           rapid reactions: Dehydrochlorination of 1,3-dichloro-2-propanol to
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Cesar A. de Araujo Filho, Shuyana Heredia, Kari Eränen, Tapio Salmi
      Epichlorohydrin is an important chemical intermediate, which can be obtained by valorisation of glycerol, an inexpensive raw material obtained as a stoichiometric co-product from biodiesel production. A continuous milliscale tubular reactor was developed to conduct the synthesis of epichlorohydrin and to measure the very rapid reaction kinetics. 1,3-dichloro-2-propanol (αγ-DCP) was dehydrochlorinated with sodium hydroxide at 30–70°C. The residence times in the millireactor system were less than 25s. The kinetic data were interpreted with a plug flow model and a rate equation based on a plausible reaction mechanism. The model – the rate equation and the plug flow concept – gave a perfect description of the experimental data.

      PubDate: 2016-04-20T16:31:25Z
  • Hydrogen by sorption enhanced methane reforming: A grain model to study
           the behavior of bi-functional sorbent-catalyst particles
    • Abstract: Publication date: 31 July 2016
      Source:Chemical Engineering Science, Volume 149
      Author(s): Ilaria Aloisi, Nader Jand, Stefano Stendardo, Pier Ugo Foscolo
      This work utilizes a previously developed particle grain model (PGM) for carbon dioxide CaO-based sorbents, properly integrated to describe numerically the behavior of a single particle where some catalytic activity is combined to the sorption function. In this way, the model capability is extended to the investigation of a bi-functional sorbent-catalyst particle for sorption enhanced steam methane reforming (SE-SMR) processes to produce hydrogen. The kinetic description of carbon dioxide capture by calcium oxide is assumed to be that successfully validated in a previous work by means of dynamic carbonation data obtained with calcined dolomite particles of different size fluidized by a N2/CO2 gas mixture. Further simulations presented here show the ability of the sorption model to describe faithfully the additional influence of temperature, carbon dioxide concentration in the gas phase and number of solid carbonation cycles. A state of the art methane and water gas shift kinetic model is utilized to predict the particle catalytic activity in the sorption enhanced reaction process. A numerical procedure is developed in MATLAB® to integrate over time and particle radius the model equations, assuming that small particles, of the order of those of interest for fluidized bed reactors (d p =500μm), are in contact with different gas phases of constant composition. The results show that conversion of the sorbent grains and the increasing thickness of the calcium carbonate layer around them make carbon dioxide sorption and methane reforming rate strong functions of residence time of particle in the reacting atmosphere, with different scenarios for the interaction between catalytic steam reforming and CO2 sorption. The model predicts that, with sufficient amount of calcium oxide inside the particle, conditions exist where the time averaged rates of carbon dioxide sorption, methane reforming and water gas shift, respectively, are such that a perfect balance exists between carbon dioxide captured by the solid phase and CO+CO2 produced by the reforming reactions.

      PubDate: 2016-04-20T16:31:25Z
  • Oxygen sorption/desorption behavior and crystal structural change for
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Hiroshi Ikeda, Soichiro Nikata, Erika Hirakawa, Akinori Tsuchida, Norio Miura
      This paper aims to elucidate oxygen sorption/desorption behavior accompanying with phase transition for perovskite-type oxide of SrFeO3−δ , as a function of temperature and oxygen partial pressure. Oxygen desorption of SrFeO3−δ in the temperature range of 100–800°C was examined in terms of oxygen non-stoichiometry and crystal structural change, by means of thermogravimetric analysis and Mössbauer spectroscopy. In the case of oxygen desorption in nitrogen, the oxygen content of SrFeO3−δ was reduced in a stepwise manner. Thus, three phases having oxygen-vacancy-ordered structures were observed, depending on temperature; Sr8Fe8O23 (SrFeO2.875) below 300°C, Sr4Fe4O11 (SrFeO2.75) at 300–400°C, and Sr2Fe2O5 (SrFeO2.5) above 400°C. In contrast, in the case of oxygen desorption in air, the oxygen content decreased monotonically with increasing temperature without appearance of any stable phases. Furthermore, the isothermal oxygen sorption/desorption behavior of SrFeO3−δ was examined to evaluate the capability as an oxygen sorbent for the high-temperature pressure-swing adsorption (HT-PSA) process. The sample sorbed oxygen in air and desorbed it in nitrogen reversibly at a constant temperature above 300°C. The oxygen-storage capacity based on the reversible weight change exhibited rather large value above 400°C, due to the large difference in its oxygen content between in air and in nitrogen. Actual oxygen separation from atmospheric air was performed at 600°C by means of the small-scale HT-PSA apparatus loaded with the SrFeO3−δ pellet-sample. The result suggests that SrFeO3−δ is one of potential oxygen sorbents for the HT-PSA process.

      PubDate: 2016-04-12T20:40:47Z
  • Numerical study of the dissolution of carbon dioxide in an ionic liquid
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Melek Sekerci-Cetin, Omer Baris Emek, Emine Elif Yildiz, Betul Unlusu
      This work investigates the dynamics of the dissolution of carbon dioxide in an ionic liquid using a computational fluid dynamics model. The system is composed of liquid and gas phases separated by a moving boundary. The transport process comprises only one-way mass transfer (from gas phase to liquid phase) since the solubility of ionic liquids in carbon dioxide is immeasurably low in general. The model accounts for the changes in the position of the liquid free-surface and liquid phase molar volume during the dissolution process. Thermodynamic equilibrium condition is valid at the liquid-vapor interface where the discontinuity in the mole fraction of carbon dioxide is formulated using the concept of internal boundary condition. The model is applied to the experimental data obtained for the [bmim][BF4]–CO2 system at 323.15K and 50bar. The binary diffusivities are calculated and compared with those obtained from the literature and some correlations.

      PubDate: 2016-04-12T20:40:47Z
  • Table of Contents
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146

      PubDate: 2016-04-08T09:51:41Z
  • Editorial Board
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146

      PubDate: 2016-04-08T09:51:41Z
  • An effective computation strategy for assessing operational flexibility of
           high-dimensional systems with complicated feasible regions
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Vincentius Surya Kurnia Adi, Rosalia Laxmidewi, Chuei-Tin Chang
      The volumetric flexibility index ( FI v ) of a chemical system can be viewed geometrically as the ratio between the hypervolume of feasible region and that of a hypercube bounded by the expected upper and lower limits of uncertain process parameters. Although several methods have already been developed to compute FI v , none of them are effective for solving the high-dimensional problems defined in nonconvex, non-simply connected or disconnected regions. While the available shortcut approaches are not accurate enough, successful tuning of the algorithmic parameters is mandatory for producing credible estimates with the more elaborate existing strategies. The above practical issues in volume estimation are thoroughly addressed in the present research. The most critical step in the proposed procedure is to characterize the feasible region accurately. To this end, the domain boundaries in parameter space are first identified with the feasible proximity points obtained by following a random line search algorithm. The Delaunay triangulation technique is then implemented to generate simplexes on the basis of such near-boundary points. By checking the centroids of these simplexes, the infeasible ones may be identified and eliminated. Finally, the hypervolumes of all feasible simplexes are summed to determine the volumetric flexibility index. Extensive case studies with 2–7 uncertain parameters have been carried out to show the superior capabilities of the proposed computation strategies.

      PubDate: 2016-04-04T16:12:01Z
  • Low-pressure performance evaluation of CO2, H2O and CH4 on Li-LSX as a
           superior adsorbent for air prepurification
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Franklin E. Epiepang, Jianbo Li, Yingshu Liu, Ralph T. Yang
      High-volume production of oxygen and nitrogen from atmospheric air is accomplished by cryogenic distillation. Prior to feeding to the air separation unit, the ambient air must be pre-purified by the removal of trace impurities such as CO2, H2O vapor, and light hydrocarbons (e.g., CH4) to their tolerable limits of 1.0ppm, 0.1ppm, and to a few ppb, respectively. In this study, the adsorption characteristics of a synthetic zeolite, Li-LSX (where LSX denotes low-silica type-X zeolite where Si/Al=1), for the removal of trace amounts of CO2, CH4, and H2O vapor impurities were analyzed and compared with the conventional synthetic 13X zeolite that has been used for air prepurification as well as the ion-exchanged K-LSX and Ca-LSX zeolites. Isotherms to very low partial pressures (to a few ppm of 1atm) were measured. The Tὸth, Langmuir–Freundlich (L–F), and the Dubinin–Astakhov (D–A) isotherm models were used to correlate the low pressure experimental data and the Tὸth model was found to be the better fit especially in the low pressure range. The superior adsorption properties of Li-LSX for air prepurification are demonstrated in this work.

      PubDate: 2016-04-04T16:12:01Z
  • A study of pressure drop in reticulated ceramic sponges using direct pore
           level simulation
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): P. Parthasarathy, P. Habisreuther, N. Zarzalis
      New values for the viscous and inertial coefficients of the Ergun equation to calculate the pressure drop within open cell ceramic sponges made of alumina and silicon infiltrated silicon carbide (SiSiC) are provided based on the direct pore level simulations (DPLS) results. The fluid flow through ceramic structures of different cell densities and porosities are simulated using standard Navier–Stokes equation without any simplification. The computational grid data are reconstructed from three-dimensional computer tomography scans of different reticulated porous media. Influence of tortuosity on the pressure drop is included in a Ergun equation based pressure drop correlation. The new correlation is dependent on the sponge properties such as, cell diameter, specific surface area and flow tortuosity.

      PubDate: 2016-04-04T16:12:01Z
  • Partial oxidation of methane on a nickel catalyst: Kinetic Monte-Carlo
           simulation study
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Sirawit Pruksawan, Boonyarach Kitiyanan, Robert M. Ziff
      Kinetic Monte-Carlo simulation is applied to study the partial oxidation of methane over a nickel catalyst. Based on the Langmuir–Hinshelwood mechanism, the kinetic behavior of this reaction is analyzed and the results are compared with previous experiments. This system exhibits kinetic phase transitions between reactive regions with sustained reaction and poisoned regions without reaction. The fractional coverages of the adsorbed species and the production rates of H2, CO, H2O, and CO2 are evaluated at steady state as functions of feed concentration of the methane and oxygen, and reaction temperature. The influence of lattice coordination number, diffusion, and impurities on the surface is also investigated. The simulation results are in good agreement with the experimental studies where such results are available. It is observed that when the lattice coordination number is increased to eight, the width of the reactive region increases significantly. Moreover, the phase transition becomes continuous. The diffusion of adsorbed O and H on the surface plays a measurable role in the reaction, increasing the maximum production rates as the diffusion rate increases. In systems with impurities, the production rates are greatly reduced and the phase transition is also changed from being abrupt to continuous.
      Graphical abstract image

      PubDate: 2016-04-04T16:12:01Z
  • Mesoscale model for heterogeneous catalysis based on the principle of
           compromise in competition
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Wen Lai Huang, Jinghai Li
      Heterogeneous catalysis is vital in modern industries, and its basic problems always attract intense academic interest. The heterogeneous distributions of adsorbates on catalyst surfaces violate the mean field assumption and relevant macroscopic models. On the other end, microscopic models are commonly unacceptable for practical spatiotemporal scales. Therefore, mesoscale models are especially desirable, which capture the essential structural features at the mesoscale with acceptable computational cost. The present work proposed a new mesoscale model for heterogeneous catalysis, based on conservation relationships and a stability condition that was built from the principle of compromise in competition. In the conservation equations variables accounting for structural heterogeneity are incorporated, and thus the equations are not closed, so a stability condition is necessary to act as an additional constraint. Following the principle of compromise in competition, two structural quantities are identified, which exhibit mutually competing tendencies, roughly corresponding to two competing mechanisms, and depending on various kinetic processes. A combination (reflecting the compromise) of these two tendencies forms the additional constraint to close the conservation equations. The relative dominance of the two tendencies can be described more accurately via including kinetic constants. Since there is no time in this model, the steady states (including structural and apparent quantities) can be achieved readily with no need of time evolution, and thus the computational cost may be even lower than that of macroscopic models. Results in various cases have been compared with those of kinetic Monte Carlo simulations.
      Graphical abstract image

      PubDate: 2016-04-04T16:12:01Z
  • A novel bimetallic MIL-101(Cr, Mg) with high CO2 adsorption capacity and
           CO2/N2 selectivity
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Zhenyu Zhou, Liang Mei, Chen Ma, Feng Xu, Jing Xiao, Qibin Xia, Zhong Li
      A novel bimetallic MIL-101(Cr, Mg) was successfully synthesized for the first time by doping Mg during the solvothermal synthesis of MIL-101(Cr), and then characterized. The doped magnesium was homogeneously dispersed in the crystals of MIL-101(Cr, Mg). The magnesium ions had successfully coordinated with the carboxylic group in BDC through Mg–O. The synthesized MIL-101(Cr, Mg) remained excellent moisture-stability after exposed to humid air with 90% relative humidity for 30 days. Importantly, Mg doping not only made MIL-101(Cr, Mg) had higher surface area than MIL-101(Cr), but also created new and strong adsorptive sites for CO2 confirmed by TPD experiments. As a result, CO2 adsorption capacity of MIL-101(Cr, Mg) was significantly improved, and reached 3.28mmol/g at 298K and 1bar, having an increase of 40% in comparison with MIL-101(Cr). More importantly, the CO2/N2 adsorption selectivity of MIL-101(Cr, Mg) was significantly enhanced up to 86 at 100kPa, being ~4 times of that of MIL-101(Cr). The strategy of doping metal ions can be an effective way to improve the adsorption performance of MOFs.
      Graphical abstract image

      PubDate: 2016-04-04T16:12:01Z
  • Numerical simulation of nonlinear chromatography with core–shell
           particles applying the general rate model
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Shamsul Qamar, Fouzia Abdul Sattar, Javeria Nawaz Abbasi, Andreas Seidel-Morgenstern
      Core–shell particles allow highly efficient and fast separation of complex samples. They provide advantages over fully porous particles, such as highly efficient separation with fast flow rate due to shorter diffusional path length in particle macropores. On the other hand, capacities are reduced due to the inert core. This work is focused on the numerical approximation of a nonlinear general rate model for fixed-beds packed with core–shell particles. The model equations consider axial dispersion, interfacial mass transfer, intraparticle diffusion, and multi-component Langmuir isotherm. A semi-discrete high resolution flux-limiting finite volume scheme is proposed to accurately and efficiently solve the model equations. The scheme is second order accurate in axial and radial coordinates. The resulting system of ordinary differential equations (ODEs) are solved by using a second-order TVD Runge–Kutta method. For illustration, a few selected scenarios of single solute and multi-component elution bands are generated to study theoretically the effects of the core radius fractions on the course of elution curves. Typically applied performance criteria are evaluated for identifying ranges of optimum values of the core radius fraction.

      PubDate: 2016-04-04T16:12:01Z
  • Application of magnetic bearing technology in high-speed centrifugation
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Manuel Konrath, Julie Gorenflo, Nils Hübner, Hermann Nirschl
      Centrifuges represent a well-established tool in separation technology to handle high throughputs of suspensions with micron-sized particles. However, extraordinarily high centrifugal accelerations are required for even smaller particles. For this purpose, we make use of magnetic bearing and drive technology. We report the first application of this contactless technique in separation experiments. The presented prototype is based on a semi-continuous principle, where sediment is built up within the rotor while the liquid (which contains the fine fraction in case of classification) is discharged at the overflow weir. The new centrifuge allows rotational speeds of more than 64kmin−1. A broad variation of parameters with centrifugal accelerations of up to C=100,000 and flow rates of up to 0.4l/min provides a sound experimental basis for this study. The cut size and the product loss of three particle systems between 10nm and 1µm (silver nanoparticles, silica nanoparticles, and polystyrene) are precisely adjustable via the mentioned parameters. Furthermore, a good comparability with a commercially available device was found regarding the specific efficiency. We consider our approach to be a promising contribution to nanoscale separation technology where scalable high-throughput methods are rare.

      PubDate: 2016-04-04T16:12:01Z
  • Modified shear stress transport model with curvature correction for the
           prediction of swirling flow in a cyclone separator
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Yaser H. Alahmadi, Andrzej F. Nowakowski
      The paper investigates the confined swirling flow in a cyclone. The numerical simulations are performed using a proposed eddy viscosity turbulence model, which accounts for the effects of the streamline curvature and rotation. This distinguishes the current model from the conventional Eddy Viscosity Models (EVMs) that are known to fail to predict the Rankine vortex in swirling flows. Although computationally more expensive approaches, the Reynolds Stress Model (RSM) and Large Eddy Simulation (LES), have demonstrated a high capability of dealing with such flows, these techniques are often unsuited for use in complex design studies where computational speed and robustness are key factors. In the present approach, the Shear Stress Transport with Curvature Correction (SSTCC) turbulence model is modified by the introduction of the Richardson number to account for the rotation and curvature effects. The numerical predictions were validated using experimental results and also compared to the data obtained using the RSM model and various EVMs without the proposed modifications. The investigations started with a benchmark case of a flow through a channel duct with a U-turn, after which more challenging simulations of a high swirling flow within a cyclone separator device were performed. The results show that the proposed model is competitive in terms of accuracy when compared to RSM and proves to be superior to the RSM model in terms of computational cost. Furthermore, it is found that the proposed model preserves the ability to represent the Rankine vortex profile at different longitudinal levels of the cyclone. It is also more efficient in terms of the computational cost than the SSTCC model without the introduced modifications.
      Graphical abstract image Highlights

      PubDate: 2016-04-04T16:12:01Z
  • Thermomechanical analysis of coal ash fusion behavior
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Tinggui Yan, Lingxue Kong, Jin Bai, Zongqing Bai, Wen Li
      Ash fusion behavior relates to several key issues for designing and running boilers or gasifiers, including fouling, sintering or slagging. In order to illustrate the mechanism of ash fusion behavior, the ash fusion temperature test, thermomechanical analysis (TMA), the high temperature processing microscope (HTPM) and differential scanning calorimetry (DSC) were applied to describe the ash fusion process and the characteristics of fusion temperatures. In addition, the thermodynamic software FactSage™ was used to reveal the relation between liquid phase formation and ash fusion behaviors. The shrinkage trace by TMA not only indicated the ash fusion temperatures, but also described the fusion process quantitatively. The ash fusion process can be divided into sintering, primary fusion and the free liquid stage based on the shrinkage trace, which was supported by HTPM and DSC results. Stage I (sintering stage), in which sintering was initialized by the formation of an initial eutectic, was characterized as the liquid phase sintering stage. The initial temperature of sintering stage is essential to prevent ash sintering or fouling. In stage II (primary fusion stage), most of the solid minerals melted and the formation rate of the liquid phase reached its maximum. The range of the plateau in this stage is determined by the end points of sintering and newly formed eutectics. During stage III (free liquid stage), the remaining solids dissolved in the liquid slag and influenced the flow behavior of slag at high temperatures. Overall, the ash fusion mechanism “Sintering-fusion-dissolving” was proposed according to the fusion behavior. The end points of the sintering and primary stage, denoted as T s1 and T s2, agreed well with deformation temperature and flow temperature, respectively. T s1 or deformation temperature should be used as key criteria to prevent sintering in boilers and gasifiers.

      PubDate: 2016-04-04T16:12:01Z
  • Prediction of mutual diffusion coefficients in binary liquid systems with
           one self-associating component from viscosity data and intra-diffusion
           coefficients at infinite dilution
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Q. Zhu, C. D'Agostino, M. Ainte, M.D. Mantle, L.F. Gladden, O. Ortona, L. Paduano, D. Ciccarelli, G.D. Moggridge
      A new model for prediction of mutual diffusion coefficients is proposed over the whole composition range for binary liquid systems of one self-associating component and one non-polar component. The model is based on the Darken equation with the knowledge of intra-diffusion coefficients at infinite dilution of both species and viscosity data for the system, and takes into account the cluster diffusion approach with a scaling power on the thermodynamic correction factor. The model was validated to show good concurrence with the experimental mutual diffusion data. Following the analysis that the mutual diffusion coefficients at infinite dilution can be identified with the molecular intra-diffusion coefficient of the species (i.e., the intra-diffusion coefficient at infinite dilution in the absence of self-association), the proposed equation was extended to binary liquid systems without significant association. The accuracy of prediction for systems of cross associating species is expected to be limited. The model relies on the knowledge of the viscosity of the mixture over the whole composition range and may be used as a valid alternative to models based on measuring intra-diffusion coefficients as a function of composition. Indeed, such data are not always available or are more difficult to obtain whereas viscosity measurements can be readily available and more easily measured.

      PubDate: 2016-04-04T16:12:01Z
  • How to select an optimal surfactant molecule to speed up the
           oil-detachment from solid surface: A computational simulation
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Xiaofang Li, Qingzhong Xue, Lei Zhu, Yakang Jin, Tiantian Wu, Qikai Guo, Haixia Zheng, Shuangfang Lu
      Using molecular dynamics simulations, we have investigated the process of oil molecules detachment from dolomite surface in different surfactant solutions (anionic, cationic, nonionic, amphoteric). The effect of surfactant molecules on the process of oil detachment from dolomite surface is extensively examined. We demonstrated that oil detachment time in nonionic surfactant solution is about 4 times of that in anionic surfactant solution and cationic surfactant solution, and oil detachment time in amphoteric surfactant solution is about 6 times of that in anionic surfactant solution and cationic surfactant solution for dolomite surface. Secondly, the process of oil detachment from four kinds of mineral models (silica modified with carboxy groups, calcite, dolomite, siderite) in nonionic surfactant solution is also studied in this paper. The results demonstrate that the oil detachment time from calcite surface is about 30 times of that from dolomite surface in nonionic surfactant solution. It is demonstrated that the optimal surfactant molecule can speed up the oil detachment from a solid surface. In summary, this work provides a feasible route to choose and achieve a better oil-displacing agent based on the interaction energy between the oil molecules and solid surface, which is also important for shortening oil detachment time and contributes to its applications in cleaning fields.

      PubDate: 2016-03-30T03:02:04Z
  • Global optimization of heat exchanger networks using a new generalized
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Sung Young Kim, Miguel Bagajewicz
      We present an extension of a previously presented superstructure (Floudas et al., 1986) for heat exchanger network grassroots design. This extension is such that it includes several matches between two streams, activates splitting control and allows for mixing temperature control. We solve this model globally using RYSIA, a recently developed method bound contraction procedure (Faria and Bagajewicz, 2011a, 2011b, 2011c; Faria et al., 2015). We also add a new RYSIA feature called Lifting Partitioning. Results show structures that cannot be obtained using the stages model (Yee and Grossmann, 1990) or other similar restrictive models.

      PubDate: 2016-03-26T04:46:40Z
  • Simple method for measuring the spectral absorption cross-section of
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Razmig Kandilian, Antoine Soulies, Jeremy Pruvost, Benoit Rousseau, Jack Legrand, Laurent Pilon
      The spectral absorption cross-section of microalgae is an essential parameter in modeling the microalgae metabolism and growth kinetics as well as in estimating the productivity and efficiency of photobioreactors. This paper presents a simple experimental procedure for retrieving the average spectral absorption cross-section of concentrated microalgal suspensions. The method combines experimental measurements of the normal–hemispherical transmittance and reflectance of the suspensions in conventional cuvettes with an inverse method and analytical expressions obtained from the modified two-flux approximation accounting for absorption and multiple scattering. The method was validated with direct measurements of the scattering phase function and of the absorption and scattering cross-sections of freshwater microalgae Chlorella vulgaris. It was able to retrieve the absorption cross-section with acceptable accuracy. The latter was then used to estimate successfully the fluence rate using a simplified light transfer model, the local rate of photon absorption, and the biomass productivity in flat plate PBRs.

      PubDate: 2016-03-26T04:46:40Z
  • Magnetic resonance imaging of gas dynamics in the freeboard of fixed beds
           and bubbling fluidized beds
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): C.M. Boyce, N.P. Rice, J.F. Davidson, A.J. Sederman, J.S. Dennis, D.J. Holland
      Magnetic resonance imaging (MRI) was used to measure directly gas velocity and gas velocity distribution in the freeboard region of a fluidized bed (52mm dia.) under bubbling fluidisation and just below minimum fluidisation. The bed consisted of poppy seed particles 1.1mm in diameter and was fluidized using SF6 gas at 7.5barg for MRI purposes. In the system, bubbles approximately 20mm in diameter rose through the centre of the bed. In the case of bubbling fluidisation, time-averaged velocity maps at different vertical positions in the freeboard showed downward moving gas in the centre of the bed and upward moving gas near the walls for this particular bed. However, below minimum fluidisation conditions, the profiles of gas velocity in the freeboard were flat, with respect to the radial dimension, with minor and random spatial variance, indicating that the profiles observed during bubbling arose from bubble breakthrough. The reasons for these observed patterns of flow are discussed.

      PubDate: 2016-03-26T04:46:40Z
  • A multi-region model for reaction–diffusion process within a porous
           catalyst pellet
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Hua Li, Mao Ye, Zhongmin Liu
      In this paper, a multi-region model based on the unified Maxwell–Stefan diffusion theory is developed to investigate the reaction–diffusion processes within catalyst pellets formed by micro-pore particles and meso/macro-pore support. The corresponding partial differential equation (PDE) systems, describing chemical reactions, bulk diffusion, Knudsen diffusion, surface diffusion and viscous flow, are converted to ODE systems based on finite volume method (FVM). The resulting multi-scale ODE systems are solved by reduced storage matrix method, where a quasi-stationary state assumption is adopted in the numerical solution to solve multi-scale problem in which the diffusivities of micro-pores and meso/macro-pores are significantly different. The alkylation of benzene over a single multi-porous pellet formed with H-ZSM-5 crystal particles was simulated as an example. The effects of volume fraction, size and spatial distribution of H-ZSM-5 crystal particles on the effectiveness factor of the catalyst pellet were then investigated and discussed. It is shown that the multi-region model is a potential bottom to up tool for reaction–diffusion processes in catalyst pellet exhibiting multi-scale time characteristic.

      PubDate: 2016-03-26T04:46:40Z
  • Bubble dynamic wave velocity in fluidized bed
    • Abstract: Publication date: 22 June 2016
      Source:Chemical Engineering Science, Volume 147
      Author(s): Liping Wei, Youjun Lu
      Experimental and numerical investigations have validated that the supercritical water (SCW) fluidized bed has bubbling fluidization state, which obviously diverges from the classical gas–solid fluidized bed. It is difficult to apply the classical bubbling parameters including diameter and rising velocity to characterise the bubbles within the SCW fluidized bed due to the unattainable measurements in the high temperature and pressure conditions. This paper derived bubble dynamic wave (BDW) velocity to establish a theoretical description of the bubbling characteristics for different bubbling systems. The BDW velocity is a propagation velocity of interface wave between bubble and emulsion phase induced by the perturbation of bubble volume. The expression of the BDW velocity was derived by treating emulsion phase as compressible fluid. The BDW velocity of the SCW fluidized bed (intermediate fluidization) shows an intermediate value between air or steam–solid system (classical bubbling fluidization) and ambient water–solid system (classical homogenous fluidization). Further, the BDW energy was derived to characterise the fluid dynamic in meso-scale. The variation trend of BDW energy with superficial velocity was consistent with that of the measured meso-scale energy of differential pressure fluctuation signals. This paper provided a new parameter of BDW velocity for describing the characteristics of bubbling fluidized bed.
      Graphical abstract image

      PubDate: 2016-03-26T04:46:40Z
  • Hydrodynamics and particle motion in upward flowing dense particle
           suspensions: Application in solar receivers
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Pablo García-Triñanes, Jonathan Seville, Benjamin Boissière, Renaud Ansart, Thomas Leadbeater, David Parker
      Dense gas–solid suspensions have the potential to be applied as heat transfer fluids (HTF) for energy collection and storage in concentrated solar power plants. At the heart of these systems is the solar receiver, composed of a bundle of tubes which contain the solid suspension used as the thermal energy carrier. In the design investigated here, the particles form a dense upward-flowing suspension. Both density of the suspension of these particles and their movement have a strong influence on the heat transfer. An apparatus was designed to replicate the hydrodynamic and particle motion in the real solar energy plant at ambient temperature. The governing parameters of the flow were established as the solid feeding flow rate, the fluidisation velocity, the solids holdup, the freeboard pressure and the secondary air injection (aeration) velocity. In the case studied, aeration was applied with air introduced into the uplift transport tube some way up its length. This study finds that the amount of this secondary air injection is the most important parameter for the stability and the uniform distribution of the solids flow in the tubes. Solids motion was measured using the non-invasive positron emission particle tracking (PEPT) technique to follow the movement of a 60µm tracer particle, onto which was adsorbed the positron emitting 18F radioisotope. Analysis of the resulting three-dimensional trajectories provides information on solids flow pattern and solids velocity. Results show the overall behaviour of the bulk material in detail: small step-wise movements associated with bubble motion superimposed on a general trend of upward flow in the centre and downward flow close to the walls. These findings suggest that this particular type of flow is ideal for transporting energy from the walls of the solar receiver tubes.
      Graphical abstract image

      PubDate: 2016-03-22T17:37:42Z
  • Synthesis of highly stable graphene oxide membranes on polydopamine
           functionalized supports for seawater desalination
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Kai Xu, Bo Feng, Chen Zhou, Aisheng Huang
      It is well known that graphene oxide (GO) is highly stable in air or water. However, the stability of asymmetric graphene oxide (GO) membrane depends on the chemistry of the support and also the thickness of the targeted coated GO layer. It is found that the GO membranes prepared on porous Al2O3 supports are unstable, and easy to crinkle and finally peel off from the support surface in a short time due to poor interaction with the support surface. In the present work, we have successfully prepared highly stable, permselective and reproducible GO membranes for seawater desalination by using polydopamine (PDA) as a novel covalent linker. Attributing to the high adhesive ability of PDA, GO nanosheets are attracted and bound onto the support surface, thus remarkably enhancing the stability of the GO membranes. It is found that the developed GO membranes are very promising for seawater desalination. For desalination of 3.5wt% seawater at 90°C, high water fluxes of 48.4kgm−2 h−1 and high ion rejections of over 99.7% can be obtained for the GO membrane which are much higher than those obtained from conventional porous inorganic membranes.
      Graphical abstract image

      PubDate: 2016-03-17T08:40:26Z
  • Study of the hydrodynamics and mass transfer in a rectangular air-lift
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Stanimir Drandev, Kalin I. Penev, Dimitre Karamanev
      Despite the increasing importance of air-lift reactors, very little published information is available on how the ratio of aerated to non-aerated cross-sectional areas (A d /A r ) of the reactor, and the aerating system affect the oxygen mass transfer and other performance characteristics. The influence of the ratio of cross-sectional areas of downcomer to riser (A d /A r ), and the type of gas-distributor on volumetric oxygen mass-transfer coefficient, gas holdup, and liquid circulation velocity were investigated in a 114L rectangular air-lift reactor with motile baffle, separating aerated from non-aerated compartments. The results indicated that the oxygen mass transfer characteristics of rectangular air-lift reactor are better at A d /A r of 2.0; the gas holdup and liquid circulation time showed maximum values at the same ratio. A new empirical model for the effects of the aeration rate and A d /A r ratio was proposed to account for the observed changes of volumetric oxygen mass transfer coefficient. The model took into account the different mixing patterns in the reactor for both cases: A d /A r ≤1 and A d /A r >1 using a wide range of these ratios.

      PubDate: 2016-03-13T08:38:12Z
  • Effects of heat treatment on the atomic structure and surface energy of
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): George Okeke, Robert Bryan Hammond, Simon Joseph Antony
      Nanomaterials have become a widely used group of materials in many chemical engineering applications owing to their ability to provide an enhanced level of functional properties compared to their crystalline and bulk counterparts. Here we report fundamental level advancements on how the anatase and rutile phase of TiO2 nanoparticles chemo-thermally respond between room temperature and the melting temperature under both vacuum and water environments. The current study is based on using molecular dynamics (MD) simulations. We present results on the equilibrium crystal morphology of these phases, structural and surface energy of TiO2 nanoparticles in the size range of 2–6nm under different temperatures. Thermodynamic and structural properties, in the form of potential energy and Radial Distribution Functions (RDF’s) respectively, are calculated for both forms of TiO2 nanoparticles. The temperature associated with the melting transition increased with an increase in the particle size in both the phases. The potential energy change associated with the melting transition for anatase was seen to be less than that for rutile nanoparticles. Also the temperature at which the RDF’s began to stretch and broaden was observed to be lower for the case of anatase than rutile, suggesting that rutile attains the most thermal stable phase for the nano particle sizes considered in this study. Structural changes in anatase and rutile nanoparticles under different temperatures revealed that non-spherical (rod-like) rutile nanoparticles tend to be thermodynamically more stable. Surface energy influences the shape of TiO2 nanoparticles at different temperatures. The increase in the surface energy of nanoparticles under vacuum when compared with that of water environment is higher for the anatase phase than the rutile phase of nanoparticle sizes studied here. The fundamental level simulation results reported here provide a strong platform for potentially accounting for the effects of atomic-scale phase characteristics of TiO2 nanoparticles and surface energy under different temperature fields in nano processing applications and related multi-scale modelling approaches in future.
      Graphical abstract image

      PubDate: 2016-03-13T08:38:12Z
  • Rapid and repeatable methane storage in clathrate hydrates using
           gel-supported surfactant dry solution
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Liang Yang, Guomin Cui, Daoping Liu, Shuanshi Fan, Yingming Xie, Jian Chen
      Gel-supported surfactant dry solution (GDS) was prepared by mixing gelling agent, sodium dodecyl sulfate (SDS) solution, hydrophobic silica nanoparticles and air in a high speed blender. GDS has the merits of surfactant dry solution (DS) and gel-supported dry water (GDW). The stack of micron-sized GDS droplets provides abundant gas transport channels and large surface area for gas–liquid contacting. Each droplet is a micro system with active surface and gelling structure. Methane storage in clathrate hydrates using GDS was investigated in a stainless steel vessel without stirring under the condition of 5.0MPa and 273.15K. The results demonstrated that the dispersed GDS droplets could significantly enhance formation kinetics, storage capacity and storage repeatability of methane hydrate. In addition, GDS exhibited faster storage rate (4.5221m3 m−3 min−1) and higher storage capacity (152.23m3 m−3) than GDW. Compared with SDS-DS, GDS has similar storage rate and better storage repeatability (by experiment of 9 cycles), but its storage repeatability slightly became poor and capacity decay occurred due to the agglomeration of droplets after these cycles of hydration/dissociation.
      Graphical abstract image

      PubDate: 2016-03-08T02:21:38Z
  • Anode partial flooding modelling of proton exchange membrane fuel cells:
           Optimisation of electrode properties and channel geometries
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Lei Xing, Qiong Cai, Xiaoteng Liu, Chunbo Liu, Keith Scott, Yongsheng Yan
      A two-dimensional, along-the-channel, two-phase flow, non-isothermal model is developed which represents a low temperature proton exchange membrane (PEM) fuel cell. The model describes the liquid water profiles and heat distributions inside the membrane electrode assembly (MEA) and gas flow channels as well as effectiveness factors of the catalyst layers. All the major transport and electrochemical processes are taken into account except for reactant species crossover through the membrane. The catalyst layers are treated as spherical agglomerates with inter-void spaces, which are in turn covered by ionomer and liquid water films. Liquid water formation and transport at the anode is included while water phase-transfer between vapour, dissolved water and liquid water associated with membrane/ionomer water uptake, desorption and condensation/evaporation are considered. The model is validated by experimental data and used to numerically study the effects of electrode properties (contact angel, porosity, thickness and platinum loading) and channel geometries (length and depth) on liquid water profiles and cell performance. Results reveal low liquid water saturation with large contact angle, low electrode porosity and platinum loading, and short and deep channel. An optimal channel length of 1cm was found to maximise the current densities at low cell voltages. A novel channel design featured with multi-outlets and inlets along the channel was proposed to mitigate the effect of water flooding and improve the cell performance.

      PubDate: 2016-03-08T02:21:38Z
  • Water droplet spreading and imbibition on superhydrophilic poly(butylene
           terephthalate) melt-blown fiber mats
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): Zaifei Wang, Leonardo Espín, Frank S. Bates, Satish Kumar, Christopher W. Macosko
      Water droplet spreading and imbibition on alkaline hydrolyzed melt-blown poly(butylene terephthalate) (PBT) fiber mats is studied with both experiments and numerical simulations to elucidate the influence of surface hydrolysis. Melt-blown PBT fiber mats were exposed to a NaOH–methanol solution for controlled periods of time, resulting in surface hydrolysis of the fiber mats and the transformation of their surface wetting properties from hydrophobic to superhydrophilic. Visualization experiments reveal the influence of the hydrolysis time on the rate of droplet absorption by superhydrophilic hydrolyzed PBT fiber mats, and are used to characterize droplet spreading and imbibition. A mathematical model was employed to understand the observed spreading and imbibition behavior and the lower effective permeability seen for long hydrolysis times.

      PubDate: 2016-03-08T02:21:38Z
  • Granular dynamics of cohesive powders in a rotating drum as revealed by
           speckle visibility spectroscopy and synchronous measurement of forces due
           to avalanching
    • Abstract: Publication date: 2 June 2016
      Source:Chemical Engineering Science, Volume 146
      Author(s): H. Yang, G.L. Jiang, H.Y. Saw, C. Davies, M.J. Biggs, V. Zivkovic
      We have used speckle visibility spectroscopy (SVS) and synchronized force measurements to compare the granular dynamics of two cohesive lactose powders, with Sauter mean diameters of ~29 and ~151μm, in a rotating drum. A load cell (LC) was used to measure forces on the drum mounting frame and enable monitoring of bulk powder motion; SVS is a dynamic light scattering technique particularly suited for studying dynamics in dense, non-ergodic granular systems. Our results reveal that surface slumping and intermittent collisional dynamics in the bulk of the bed are correlated, especially for the fine more cohesive particles (Geldart group C/A boundary), but not as much for the less cohesive larger particles (Geldart group A/B boundary). The specific dissipation energy of the particles in the drum is similar for both powders, and increases linearly with increasing drum speed. However, the dependencies of the load cell and SVS signals on rotation speed have opposing trends for these two powders, indicating different dissipation mechanisms for the different Geldart Groups; collisional dissipation is more important for the Geldart C/A powder, while for the Geldart A/B powder avalanche dissipation is dominant.

      PubDate: 2016-03-08T02:21:38Z
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